1. Field of the Invention
This invention relates to a code generator for teleprinters or data printers which emits a sequence of character signals assigned to a subscriber for the recognition of the subscriber.
2. Description of the Prior Art
Code generators are conventionally provided in teleprinters or data printers. After the establishment of a connection between a first subscriber station and a second subscriber station, the code generator in the teleprinter or data printer of the first subscriber station is triggered, for example, by the second subscriber station after the depression of a key which initiates a call "who is there?". The code generator emits a sequence of character signals which is assigned to the first subscriber station and with the aid of which the second subscriber station is able to establish whether a correct connection has been formed. It is also possible for the code generator in the teleprinter or data printer of a subscriber station to be triggered by the subscriber himself by the depression of a "here is" key.
It is already generally known in the art to employ mechanical code generators in teleprinters or data printers. In one type of code generator the character signals are stored in comb-like components which are arranged radially on a roller. The number of comb-like components is equal to the number of character signals to be emitted by the code generator. Each comb is provided with teeth, the number of which is the same as the number of elements in one character signal. Each tooth is assigned to one data element of the character signal having a starting pulse polarity and for every data element of the character signal having a stopping pulse polarity one tooth must be extracted from the comb. The roller is moved for interrogating the character signals and contacts are opened or closed in dependence upon the presence or absence of teeth.
The known code generator has the disadvantage that mechanical intervention is required in order to modify the character signals. In addition, the code generator consumes a large amount of power due to the necessity of using a motor magnet for moving the roller. The contacts require interference suppression elements in order to ensure a satisfactory operation with the electrical units of the teleprinter or data printer. The return of the code generator to its basic position necessitates expensive procedures if, for example, during the transmission of the character signals the connection to the second subscriber is broken or the power supply, usually conventional supply means, fails. Furthermore, the known code generator has the disadvantage that it contains moving mechanical components which are subjected to wear and which give rise to noise.